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Physical evidence on the dimensions of icebergs released from the mouth of Hudson Strait into the northwest Atlantic during the last Heinrich event (H-0) is presented. Side-scan sonar imagery shows scour marks up to 700 m wide and longer than 28 km. These scour marks were carved by gigantic icebergs (megabergs) with keel drafts possibly as great as 660 m capable of scouring trenches 20 to 25 m deep into the seabed. These icebergs were likely calved from the grounding margin of a thick (possibly as thick as 640 m) rapidly-flowing glacial margin during the H-0 Heinrich event (11 ka BP). Along with the relatively few megabergs released were large numbers of smaller icebergs that calved from the ice margin at the same time and were also produced from break-up of the megabergs. Scouring of the seabed by the large and smaller icebergs happened at the same time, with megabergs scouring only in the deep waters of Hatton Basin, and the smaller bergs scouring only on the eastern, shallow margin of the Basin at the continental shelf break. 相似文献
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In order to identify the mud diapirs and mud volcanoes off SW Taiwan, we have examined ∼1500 km long MCS profiles and related marine geophysical data. Our results show ten quasi-linear mud diapirs, oriented NNE–SSW to N–S directions. Thirteen mud volcanoes are identified from the multibeam bathymetric data. These mud volcanoes generally occur on tops of the diapiric structures. Moreover, the active mud flow tracks out of mud volcanoes MV1, MV3 and MV6 are observed through the high backscatter intensity stripes on the sidescan sonar images. The heights of the cone-shaped mud volcanoes range from 65 m to 345 m, and the diameters at base from 680 m to 4100 m. These mud volcanoes have abrupt slopes between 5.3° and 13.6°, implying the mudflow is active and highly viscous. In contrast, the flat crests of mud volcanoes are due to relative lower-viscosity flows. The larger cone-shaped mud volcanoes located at deeper water depths could be related to a longer eruption history. The formation of mud diapirs and volcanoes in the study area are ascribed to the overpressure in sedimentary layers, compressional tectonic forces and gas-bearing fluids. Especially, the gas-bearing fluid plays an important role in enhancing the intrusion after the diapirism as a large amount of gas expulsions is observed. The morphology of the upper Kaoping Slope is mainly controlled by mud diapiric intrusions. 相似文献
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根据侧扫声纳影像的特征,提出了基于灰度共生矩阵(gray level co-occurrence matrix,GLCM)纹理分析的声纳影像纹理提取方法,对不同的纹理特征参数进行量化分析,生成侧扫声纳纹理图像,并建立侧扫声纳图像纹理数据库,实验结果验证了该算法的有效性和可行性。 相似文献